The R-T-B based permanent magnet (R represents a rare earth element, and T represents Fe or Fe with part of it replaced by Co) comprising a tetragonal compound R2T14B as the major phase is known to have excellent magnetic properties, and has been considered as a representative permanent magnet with good performances since it was invented in 1982 (Patent Document 1: JPS9-46008).
In particular, the R-T-B based permanent magnets in which the rare earth element R consists of Nd, Pr, Dy, Ho or Tb have large magnetic anisotropy fields Ha, and are widely used as permanent magnet materials. Of those, the Nd—Fe—B based permanent magnet having Nd as the rare earth element R is widely used in people's livelihood, industries, transportation equipment and the like, because it has a good balance among saturation magnetization Is, curie temperature Tc and magnetic anisotropy field Ha, and is better in resource volume and corrosion resistance than the R-T-B based permanent magnets with other rare earth elements R. However, the Nd—Fe—B based permanent magnet has some problems. In particular, the absolute value of the temperature coefficient of the residual flux density is large, and only a small magnetic flux can be achieved especially under a high temperature above 100° C. compared to that under room temperature.